Conditioning system for water based can sealants

ABSTRACT

A conditioning system for water based can sealing compounds comprising a pressure regulation means, such as a gravity fed supply tank adjacent a double diaphragm pump, a filter and a lining nozzle, an exit line from the nozzle connected to an upstream pressure regulator and a return line meeting the supply line between the pressure regulation means and the pump. Additionally, one or more dampeners may be added to the system as well as various pressure gauges and other sensors. The use of multiple lining nozzles on one conditioning system is also disclosed, with the nozzles being capable of independent control. The system without dampeners controls film weights to within +/-5% of the desired amount. The use of one or more dampeners improves film weight control to within +/-3% of the desired amount.

This is a continuation-in-part of application Ser. No. 07/335,624 filedon Apr. 10, 1989, now U.S. Pat. No. 4,910,369.

CONDITIONING SYSTEM FOR WATER BASED CAN SEALANTS

The present invention relates to a system for conditioning water basedcan sealants. More particularly, it relates to a system for controllingthe film weight of a water based can lining compound in a lining system.

BACKGROUND OF THE INVENTION

There are two basic groups of can lining compounds in use today; solventbased and water based.

Solvent based compounds comprise a rubber based can lining compounddissolved and/or dispersed in one or more solvents. After the compoundis lined onto a can end, the solvent is driven off to leave a resilientgasket.

Water based compounds are similar, however, the compounds are dispersedand/or emulsified in water rather than a solvent. These materialstherefore avoid the problems normally associated with solvents, such aspollution, flammability, and health effects.

Typically, both compounds are supplied under pressure to a liningnozzle. A can end, mounted to rotary chuck below the nozzle, is rotatedat a set speed. The nozzle is opened to apply the required amount ofcompound to the can end.

The key to obtain an acceptably lined can end is the sufficient andconsistent deposition of compound as defined by the film weight andplacement of the compound on the end. Film weight is the amount ofcompound that is applied to each can end. If too much is applied, theexcess compound could distort the seal causing leakage, compound iswasted and the profitability suffers. If too little is applied, the endwill not form a proper seal and leakage occurs.

Film weight can be approximately determined by the following equation:##EQU1## where FW is film weight, P is the pressure difference betweenthat contained within the lining system and the atmospheric airpressure, D is the diameter of the lining nozzle orifice, η is theviscosity of the compound as it flows through the nozzle, L is the leadlength of the nozzle, and t is the lining time. This equation has beensimplified and does not take into account other variables such as thewear of the nozzle, the configuration of the inside surface of thenozzle (tapered, etc.), the height to which the nozzle needle is liftedduring lining, transient flow response from needle opening/closing, andelastic response of the compound. However, these variables are secondaryin their effect and can, for purposes of this discussion, be ignored.

For a manufacturer of can ends, D and L are fixed for a given nozzle.Pressure and viscosity tend to vary depending on environmental effectson the system. Pressure and viscosity must be controlled and heldconstant in order to obtain consistent and sufficient film weights.

In solvent systems, the pressure and temperature are regulated by a"conditioner". This conditioning system comprises a rotary gear pump, afilter and a heater connected to the supply side of a lining nozzle anda back pressure regulator or pinch valve connected between the exit sideof the nozzle and the gear pump. Gear pumps have steady flow anddischarge pressure. Constant pressure in the system is required tomaintain consistent film weight. In order to preclude a fluctuation inpressure each time the lining nozzle is opened, the recycle system isdesigned to recirculate large amounts of compound, usually 40 to 50times the amount discharged through the nozzle. The heater isthermostatically regulated such that the temperature of the compound inthe conditioner is closely controlled. As a consequence the compoundviscosity, which is temperature sensitive, is accurately maintained. Ifthe lining system should become inoperative for an extended period oftime, the compound could make hundreds of passes through the recyclesystem. This amount of recycling is not a problem for solvent basedcompounds which are generally thermodynamically stable products.

However, water based compounds, being emulsions and/or dispersions, arenot thermodynamically stable. Water based compounds require the use ofsurface active agents or protective colloids to maintain the compound ina usable state until lined.

The close clearances associated with rotary pumps cause a great amountof shear stress on water based compounds which destabilizes thecompound, thus precluding the use of a conditioning system as is used insolvent based compounds.

This inability to condition water based compounds causes problems to thecan end manufacturer in controlling and obtaining a consistent filmweight. Fluctuations in ambient temperature which frequently occur on adaily basis, shutdowns during which the viscosity of the compoundincreases and the inability to hold the compound at a constant pressureprecludes can end manufacturers from controlling film weights at +/-10%of the desired weight, which is the standard for solvent basedcompounds. Field experience has shown that controlling film weights evenat +/-15% of the desired weight is often difficult to achieve with waterbased compounds.

The present invention overcomes the difficulties encountered with liningwater based compounds and greatly improves the film weight control ofwater based compounds.

SUMMARY OF THE INVENTION

The present invention is a system for conditioning water based compoundssuch that consistent film weights can be applied to can ends. The systemcomprises a downstream regulator or alternatively a gravity feed supplytank connected to the compound supply, a pump connected to the oppositeside of the downstream regulator or gravity feed supply tank, a filterand a heater connected between the pump and the lining nozzle, and aback pressure regulator connecting the exit port of the lining nozzle tothe inlet of the pump. The preferred embodiment uses a double diaphragmpump and contains two pressure pulsation dampeners, one locateddownstream from the pump and the other located downstream from the backpressure regulator. The conditioning system of the present inventionallows film weight control within +/-5%. The preferred embodiment of thepresent invention provides even further control to within +/-3%.

IN THE DRAWINGS

FIG. 1 is a representation of an embodiment of the present invention.

FIG. 2 is a representation of the preferred embodiment of the presentinvention.

FIG. 3 is a representation of another preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an embodiment of the present invention. The details to theleft of the dotted line represent the can end manufacturer's plant. Asupply 1 of compound from the manufacturer's storage is passed through avalve 2 and filter 3 and past drain valve 4 and into the conditioningsystem. A first pressure regulation means 5, preferably a downstreamregulator is provided near the connection of the supply to the system. Ameans for sensing pressure in the system, preferably a pressure gauge 6is located downstream from the regulation means 5. A pumping means 7,preferably a diaphragm type pump is located downstream from the pressuregauge 6. The pumping means discharges into a filtering means 8 forcollecting coagulum that may form in the system. A drain valve 9 and avalve 10 are located between the filtering means 8 and a temperaturecontrolling means 11 for the compound. The temperature controlling meansis connected to an inlet port 12 of a lining nozzle 13. The compoundwhich is not lined through the nozzle 13 is discharged through an outletport 14. A pressure gauge 15 located downstream of the outlet port 14,monitors the lining pressure of the system. A second pressure regulationmeans 16 is located downstream from the pressure gauge 15. Preferably,it is a back pressure regulator, although a pinch valve or otherrestriction may be used as well. An additional drain valve 17 and valve18 are located downstream from the second pressure regulation means 16and are connected to the system between the first pressure regulationmeans 5 and the pump 7 by a return line 19. All of the variouscomponents are connected to each other by appropriate conduit means suchas metal or plastic tubing or piping.

FIG. 2 shows a preferred embodiment of the present invention connectedto a can end manufacturer's equipment. The supply 20 is connected to apressure gauge 21 which connected to a valve 22 and a filter 23. Asecond pressure gauge 24 is located downstream of the filter 23 andadjacent a drain valve 25. The use of gauges 21 and 24 allows one tomonitor the function of the filter 23.

A downstream pressure regulator 26 is connected to the manufacturer'ssupply line. This regulator is upstream of the pump 28 and the returnline 47 from the nozzle 38. The pump 28 is then connected to a firstdampening means 29 for damping any pressure fluctuations caused by thepump 28 or other components in the system. The dampening device 29, asshown, may be attached by a valve 30 so that it may be selectivelyactuated as desired and easily removed should the device requiremaintenance. Preferably, a pressure gauge 31 is mounted to the dampeningmeans 29. A filter 32 is located beyond the dampening device. A drainvalve 33 and valve 35 are used to control the flow of the system asrequired. A pressure gauge 34 is located between the valves 33 and 35 tomonitor filter function. Beyond the valve 35 is a heater 36 for warmingthe compound to the desired temperature. The function of the heater isto maintain a constant compound temperature in the event of an ambienttemperature variation in the plant. The heater 36 is connected to theinlet port 37 of the lining nozzle 38. Unlined compound is circulatedthrough the nozzle 38 and out exit port 39. Lining pressure is monitoredby pressure gauge 40. The pressure of the system is regulated by theback pressure regulator 41 adjacent the pressure gauge 40. A seconddampening means 42 is connected by a valve 43 downstream from the backpressure regulator 41. As shown, the preferred dampening means has apressure gauge 44 attached to it for monitoring of the dampening system.A drain valve 45 and a valve 46 are located downstream from the seconddampening means 42 and are used to control the flow of the system. Areturn line 47 is attached to the system between the downstreamregulator 26 and the inlet side of the pump 28 to allow for therecirculation of compound.

The use of a gravity feed tank to supply the system is an alternativeembodiment to the use of a first pressure regulator as shown in by theembodiments of FIGS. 1 and 2. This is a useful alternative particularlywhere the first pressure regulator is designed to compensate for thesesupply pressure variations and hold the feed pressure to the pumpconstant. As the regulator wears, leakage paths can develop which reducethe ability of the first regulator to respond fully, especially duringperiods in which the lining machine is down where tight shut off isdesired.

The gravity feed tank is preferably attached to the manufacturer'ssupply by an automatic valve. The valve is also attached to a levelsensor mounted adjacent the tank. The sensor measures the level ofcompound in the tank and thus controls the actuation of the valvesupplying compound to the tank. Various sensors are well known andwidely used for controlling the level of fluid in a container.

For example, a float may be used which mechanically or electricallyoperates the valve. When the compound level reaches a lowerpredetermined limit in the tank, the float opens the valve and allowscompound to flow into the tank. When the float has risen to apredetermined upper level, the float will shut off the valve, stoppingthe supply of compound to the tank.

Another suitable sensor is known as a conductivity probe. In thisembodiment there are generally two such probes, one which senses thepreset lower limit and another for sensing the upper limit for the tank.

More preferably, the sensor is not immersed in the compound within thetank. It has been found that when the sensor, such as a float orconductivity probe, is immersed in the compound, the compound tends toadhere to the sensor over time, thus reducing the sensitivity and thereliability of the sensor.

One preferred level control device is a series of capacitance sensorswhich are preferably located on the outer surface of the tank. (Althoughif desired, one may mount the sensors on the inside wall of the tank).Preferably, three sensors are used, one to open the valve when the levelreaches a desired lower limit in the tank, a second one to close thevalve when at a high preset level and a third located above the secondwhich acts as a failsafe to shut down the conditioner and sound analarm. With the use of such sensors on the exterior of the tank, it isbelieved that a metallic tank cannot be used. A plastic tank ispreferred although a glass or a composite type of material may also beused. Additionally, although compound may eventually coat the side ofthe tank, the selected sensors preferably would be tunable so that theeffects of any such coating can be eliminated.

Another preferred level control system consists of an ultrasonic sensormounted on the inside of the tank but above the desired upper liquidlevel. The ultrasonic sensor determines the level of the fluid in thetank through the use of sound waves and opens and closes the valveaccordingly. Preferably, a failsafe sensor is also mounted near theultrasonic sensor in the event of a failure of the ultrasonic sensor.The ultrasonic sensor may be used in a metal tank or a plastic, glass orcomposite tank.

Capacitive sensors are well known and widely available. Such a sensorcan be purchased from Industrial Sensors, Newport, Mich.

An ultrasonic sensor that is preferred in the present invention can bepurchased from Industrial Sensors, Newport, Mich.

Another method of dealing with the issue of wear in the downstreamregulator as the first pressure regulating device is to use a rubberball instead of a metal one in the regulator. The rubber will cold flowand conform to the seat as the ball wears. The use of the rubber ballgreatly extends the effective life of the ball and seat.

Additional features may also be added to the system as desired. Forexample, in the event that the lining system is shut down, e.g. forproblems incurred in the supply of container closures or for otherproblems incurred in components not contained within the conditioningsystem, it would be advantageous to incorporate a signaling systembetween the lining system and the conditioning system so as to close offthe compound supply to the first regulation device. One couldincorporate an automatic shut off valve to the compound supply so thatif a problem occurs with any of the other systems which interact withthe conditioning system (e.g. lining system, closure supply andtransportation system, etc.) the supply of compound to the conditionersystem is shut off.

The above automatic shut off valve would preclude compound from bleedingpast the first regulation device if it should become worn thus furtherextending the useful life of the first regulation device such that itcan operate effectively even after substantial wear occurs. Likewisethis same shut off valve could be actuated if the air pressure suppliedto the conditioner is lost or drops too low thus protecting thediaphragms of the pump and bladders of the pulsation dampeners from highdifferential pressure that can result if compound should bleed past aworn first pressure regulation.

A preferred sensor could control a solenoid which could actuate a valvelocated in the compound supply line between the manufacturer's supplyand the beginning of the conditioning system such that upon a signalfrom the sensor, the compound supply would be shut off and/or theconditioning system shut down. Another preferred embodiment is to use asensor and electrically actuated valve.

The pumping means of the system is a pump, the moving parts of whichoperate at relatively low velocities and which have large clearances soas to have little shearing effect on the compound as it circulatesthrough the system. This prevents the viscosity and stability of thecompound from being adversely affected as it is cycled. A preferred pumpis a diaphragm type pump. More preferably, it is a double diaphragm typeof pump.

In addition to the low shear imparted to the compound, diaphragm pumpsare preferred as they do not exhibit seal problems due to friction andwear as is common with piston type pumps, progressive cavity pumps, lobepumps, etc. which can be used to pump water based compounds.Additionally, these pumps, particularly double diaphragm pumps, tend togenerate smaller pressure pulsations than single diaphragm pumps, thusreducing the pressure fluctuation that must be damped. Lastly, becauseof the mild shearing stresses, these pumps do not tend to form coagulumwhich could block the system.

Preferably, the selected pump has a low volumetric displacement/strokeso as to further minimize the magnitude of the pulsations. Additionally,the chosen pump should be selected so that it can cycle a sufficientvolume of compound through the system to avoid significant fluctuationsin the circulation compound volume due to the discharge of compound atthe nozzle. The pump preferably should be able to cycle a volume ofcompound that is from about 10 to 60 times the amount of compounddischarged through the nozzle. Typically, this would require a pumpcapable of pumping 0.1 to 0.6 gallons/minute.

Additionally, the preferred pump will have diaphragms made frompolytetrafluoroethylene or other flexible materials with a lowcoefficient of friction and a body formed from plastic such aspolypropylene or a metal such as stainless steel, so as to reduce thetendency for having coagulum that might be formed to remain inside thepump.

One such pump is sold by Yamada American, Inc. While the named pump isair actuated, other mechanically or electrically driven pumps could alsobe used.

The filter may be any filter commonly used in compound lining equipmentincluding basket type fillers, pleated filters, etc. Preferably, thefilter used in the system consists of a stainless steel wire mesh screenhaving a mesh opening of 40 per inch and which is contained with abasket type housing. Such a filter can be obtained from The Kraissl Co.of Hackensack, N.J.

The first pressure regulating means may be a downstream pressureregulator, e.g. a regulator that senses the pressure of the fluiddownstream from its position and actuates according to changes in thatpressure. This regulator tends to reduce pressure flucuations that maybe received from the can end manufacturer's supply system. Such aregulator is commercially available from the Aro Corporation of Bryan,Ohio.

Alternatively, the first pressure regulating means may be a gravity-fedtank system as described above. The tank may have an open top oralternatively it may be a closed tank. If the latter, a vent should beprovided in the top of the tank. The tank should have at least oneinlet, preferably located near the top of the tank and one outletlocated near the bottom, preferably the bottom of the tank.

Alternatively, the tank may have a movable bellows or diaphragm whichmoves relative to the volume of fluid in it so as to maintain the samepressure on the compound.

Other alternative embodiments for such a closed tank system include alevel sensing device which operates over a very narrow range of levelsso as to reduce the air flow in and out of the tank thus reducing thepossibility of skinning or coagulation. Likewise, the use of largevolume tank (i.e. large head space) and relatively small amount ofmovement of the fluid and/or bellows or diaphragm may also be used.

It is preferred that whatever system is selected, it not compress theair in the head space of the tank to any significant degree and therebynot vary the head of the fluid by any appreciable amount. By minimizingthe fluctuation in head of the fluid, one reduces the pressure variationon the compound supply to the pump.

The second pressure regulation means is a back pressure or upstreampressure regulator. It operates in a manner similar to that of thedownstream regulator, except it responds to the pressure changes of thecompound upstream from the regulator. In this instance, the backpressure regulator responds to changes in the line pressure betweenitself and the exit port of the lining nozzle. Alternatively, a pinchvalve or other restriction may be used instead of the second pressureregulator.

A suitable back pressure regulator is also available from the AroCorporation.

The purpose of the pressure regulators is to maintain the liningpressure of the system at a constant value. The preferred size of theregulator should be matched to the desired range of operating pressureand the desired flow rate of the compound in the system. The backpressure regulator does, in addition, apply a controlled shearing actionto the compound to break down any structure that may have formed.

The pair of regulators have a synergistic effect on each other and thesystem. It has been found that should the first regulator losesensitivity, the other regulator is able to compensate and regulate thepressure within the system.

It is preferred that the temperature of the compound in the conditionerbe controlled so that the film weight can be kept constant. Compoundviscosity is affected by temperature, however, if desired, one may notuse a temperature control means in the present invention. In particular,such a control means is not necessary when the ambient temperature canreasonably be controlled within the plant, such as by plant airconditioning or heating systems.

The means for controlling the temperature of the compound is preferablya heater with a controller having a variable set point. More preferably,the heater comprises a tube through which the compound circulates andwhich is heated from the outside by fluids, hot air, electricalresistance and other well known heating means. One such heater comprisesa flexible tube, formed of polytetrafluoroethylene or other suchmaterials with a low coefficient of friction so as to reduce the chanceof coagulum being trapped in the heater, which is surrounded by a jackethaving heating wires or coils mounted therein. Such a heater is capableof raising the temperature of a compound in the system by 20° F. abovethe outside ambient temperature within 30 minutes without excessivejacket temperatures and maintaining that temperature while the system isin operation.

One such heater is available from Omni Systems of Frenchtown, N.J. andcomprises a 3 foot tube of 3/8 inch (internal diameter) hose formed ofpolytetrafluoroethylene. The hose is surrounded by a jacket havingelectrical heaters (30 watts per foot) and is thermostaticallycontrolled.

The first and second damping means are preferably pressure surgesuppressors which minimize and even out pressure fluctuations in thesystem. One preferred surge suppressor has a bladder that separates achamber into two parts and a regulator for the introduction of air intothe upper portion of the chamber. Compound from the system flows intothe lower portion of the chamber. As the level of the fluid moves up anddown in the chamber due to pressure fluctuations, the regulatorautomatically permits air to flow into the upper portion of the chamberas is required to damp the pressure pulsation.

Other types of surge suppressors or pressure dampeners may be known andare useful in the present invention. For example, the pressure dampenermay be a fixed charge type of bladder dampener or a flow through type ofdampener. A fixed charge bladder dampener is similar to the preferredvariable charged dampener, however there is no regulator for theintroduction of additional air as the bladder expands or contracts.Additionally, one may use an additional downstream regulator in lieu ofthe dampener to obtain the same effect. Also, one may use a flow controlvalve which controls the flow of the compound rather than the pressureof the compound and obtain the same result.

The damping means in FIG. 2 is shown with a pressure gauge. While it ispreferable that the dampener have such a gauge, it is by no meansrequired.

One suitable dampener is sold by Wilden Pump and Engineering under thename Blacoh Sentry II (automatic version).

It is preferred that two dampeners be used in the present system,although it has been found that one dampener located on the downstreamside of the pump is sufficient in some cases to damp pressure pulsation.The additional dampener located downstream from the back pressureregulator tends to minimize any water hammer effect that might occur tothe pump by the pressurized feed of compound. This tends to increase theefficiency of the system and extend the useful life of the pump.

Additionally, one may add a pressure regulator, as described above,between the pumping means and the lining nozzle or nozzles. The additionof this regulator eliminates any pressure flucuation in the system,particularly when one is not using the preferred double diaphragm pump.Alternatively, one may use a flow control valve instead of theadditional downstream regulator. In this instance, the flow of compoundrather than the pressure is maintained constant. The addition of one ormore pressure regulators or flow control valves is of particular valuewhen one wishes to supply two lining nozzles from one conditioningsystem.

It is preferred that each of the components of the system be connectedby easily detachable means such as threaded couplings, etc. to allowdisassembly of a portion of the system when maintainance or repairs needto be made.

The piping or tubing used in transporting the compound through thesystem can be constructed of any material that is commonly used withwater based compounds. The tubing should be inert to the compound,strong, long lasting and preferably inexpensive. Typical materialsinclude steel, particularly 304 stainless steel, aluminum and variousplastics such as CPVC (chlorinated polyvinyl chloride) and high pressurepolypropylene pipe and fittings. These plastics are preferred as they donot loose appreciable strength at the temperatures encountered in thesystem.

The system may also contain various pressure sensors and/or temperaturesensors which may be displayed upon a control board so as to allow anoperator to determine the exact condition of the system at any time. Ifdesired, such sensors can be wired to an alarm so that if a malfunctionoccurs, the operator is instantly notified and remedial action can betaken.

Once the system has been connected to the manufacturer's supply line andlining nozzles and provided with the appropriate electrical andpressurized air supplies, the system is filled with compound, purged ofair, and brought to operating temperature and pressure.

The system is then essentially automatic and should only be monitoredfor changes. Changes in compound temperature and thus compound viscosityare obtained through varying the temperature of the heater temperatureis usually set about 5° to 10° F. above the maximum ambient temperatureexpected. Changes in lining pressure are obtained through adjustments tothe back pressure regulator, the pump air pressure is set initially andneed not be adjusted thereafter.

Compound from the supply will be drawn, as needed by the system, throughthe downstream regulator and into the pump. The compound then flowsthrough the first dampener, filter and heater to the lining nozzle.There a portion of the compound is discharged onto the can end. Theremaining compound is recycled to the pump where it begins its nextcycle.

In the event that the lining nozzle is closed for an extended period oftime, such as may occur when the supply of ends to be lined isinterrupted the conditioner system may continue to circulate compoundand upon restarting of the lining nozzle, the conditioner will provideconsistent film weights to the can ends. In the embodiment of FIG. 2, acommercial compound was cycled through the system for 42 hours withoutdraw off (approx. 2000 cycles). The reduction in viscosity of thecompound was insignificant. Mechanical stability and other liningcharacteristics of the compound were essentially unchanged. This testrepresented an abnormal and extreme situation. Most shutdowns will lastfrom 10 minutes to a few hours and under these circumstances, negligiblechange in viscosity of the compound will occur. If desired, one canalternatively shut down the conditioning system when the liningequipment is inoperative for more than a couple of hours and activatethe system when the lining equipment is started again. For particularlysensitive compounds, it may be prudent to do so.

While this invention has been described in relation to a one nozzlelining system, it should be pointed out that more than one nozzle may berun from the conditioning unit of the present invention.

To attach two nozzles to the system, one would merely need to divide thecompound flow at some point between the pump and the nozzle so as toprovide two compound supply lines to the two nozzles. The two nozzleoutlet ports would then be connected to a common supply line before thesecond pressure regulation means. Preferably, the compound supply lineis separated into two channels just before the lining nozzle inlet portsso that additional heaters (if used) filters, etc. are not required.

If independent pressure control of each nozzle is desired, one may do soeasily by adding a downstream regulator or flow control valve to eachbranch of the tubing adjacent the inlet port to each gun. Additionally,an upstream pressure regulator should be used on each the outlet port ofeach gun rather than using a common one as described above.

FIG. 3 shows an embodiment of the present invention which incorporatedthe gravity feed system and the multigun, independently controlledfeatures of the present invention. FIG. 3 is essentially identical toFIG. 1 except for various added or changed features. In particular, FIG.3 shows the manufacturer's supply of compound 101 supplied through avalve 102 and filter 103, past drain valve 104 and into the conditioningsystem. The compound flows through a valve 105 which is controlled bylevel sensing device 106 adjacent to or incorporated into the gravityfeed tank 107 as the first pressure regulating means. The compound isfed to the tank by an inlet 108 and drawn out of the tank 107 from thebottom by an outlet 109. From there, the compound flows through the pump110, filter 111, past drain valve 112 and through valve 113 to theheater 114 (optional). After the heater 114, if used, the line is splitinto two separate loops at a junction 115. Compound then flows throughthe parallel lines 116A and B and downstream regulators 117A and B andinto nozzles 118A and B. If desired, one may add shut off valves in eachbranch to allow one to balance the flow in the branches.

If either valve is activated, the compound flows through either nozzle118A or 118B or both. That compound which is not drawn out throughnozzles 118A or 118B flows out the respective outlet port 119A or 119B,past a second pressure regulating device, in this embodiment on upstreamregulator, either 120A or 120B, to the junction point 121 where the twocompound flows are reunited. From this point, the compound flows pastdrain valve 122, valve 123 to return line 124 to the pump 110 forrecirculation.

By using a pressure or flow regulating means on each side of therespective nozzles 118A and 118B, one is able to maintain constantpressure, shear history, temperature, etc. throughout the entire systemeven though one or both of the nozzles may be actuated, simultaneouslyor not and change the pressure in one branch or to one gun withoutaffecting the other.

One could of course use a flow control valve in lieu of the downstreamregulators, if desired.

The present invention provides several advantages to the manufacturer ofcan ends.

Most importantly, it provides improved film weight control withoutcompromising the mechanical stability, flow and sealing properties ofthe compound.

Moreover, one can control film weight by needle lift adjustment only orby pressure adjustment as well, although the balance between thebranches may be offset.

Additionally, manufacturers do not have to be concerned about ambienttemperature variation, compound shear history or variations in supplypressure as the conditioner maintains the compound at a constanttemperature, pressure and viscosity.

It is known that changes in ambient air temperatures can cause afluctuation in the film weight obtained from a system. In general, thefilm weight will vary by about 1% per °F. Therefore, a change intemperature of 20° F. during the course of a day, which is not uncommonin most parts of the world, would result in a deviation in film weightsof up to 20%.

Likewise, a change in line pressure is known to affect the film weight.In general change of 1 psi will cause about a 4% change in the filmweight obtained, when the lining pressure is in the range of 20 to 30psi, which is typical of commercial conditions.

Compound viscosity is affected by shear history, especially shutdowns,which can occur randomly or during scheduled maintenance checks or onweekends.

The present invention is unique in that it controls the effects ofpressure, temperature and shear history (since the most recent shearhistory is dominant on the system) and provides consistent film weightsdespite changes in the ambient temperature, supply pressure or shearhistory upstream. It has been determined that the present inventionallows control of compound temperature to within +/-1° F. of the desiredtemperature. Additionally, the present invention allows control ofcompound lining pressure to within +/-0.5 psi of the desired pressurelevel when the lining pressure is in the range of 20-30 psi. With suchsensitive control, the present invention has been able to negate theeffects of ambient temperature, supply pressure and shear history on thefilm weight of the compound.

Additionally, the present invention allows the can end manufacturer tovary the temperature of the compound within the system and gainadditional control in adjusting proper placement of the compound on thecan end. Varying the temperature of the compound within the systemchanges its viscosity and thus provides a different flow out of thecompound as it is lined on the can end. In this manner placement of thecompound on the can end can be altered by varying the temperature in thesystem.

The present invention also allows the compound manufacturer greaterlatitude in selecting the flow characteristics of the compound. Compoundis preferrably manufactured with a yield value so that the variouscomponents of the compounds do not settle out during transportation andstorage. Unfortunately, the yield value may affect the flow of thecompound at moderate and high shear rates as occur in the supply pipingand lining nozzles. Compounds generally represent a balance between thecharacteristics at low shear rates, moderate and high shear rates.

The present invention, due to its control of temperature and pressureand shearing action, allows the compound manufacturer to vary the lowshear rate characteristics to a greater extent as the system allows thecan end manufacturer to vary the viscosity of the compound in thesystem. Moreover, as shown in FIG. 3, the present invention allows a canend manufacturer to independently control the function of two or morelining nozzles from one conditioning system, thus making the system moreeconomical to use.

The present invention, due to its ability to provide consistent filmweights, allows the can end manufacturer to reduce the target filmweight of the compound without risk of rejecting increased numbers ofcan ends. As film weights currently vary by +/-15%, a target film weightmust be at least 15% higher than desired so as to compensate for lowfilm weight deposition. As the present invention provides a means foraccurately controlling film weights, the can end manufacturer may reducehis target film weight significantly without adversely affectingrejection rate, thus increasing profitability.

In summation, the system, without any specific damping means, is capableof damping the pressure fluctuations of the system to an extent thatfilm weight can be controlled to within +/-5% of the desired weight.This is a two fold improvement in film weight control over thatcurrently achieved in solvent compound systems and a three foldimprovement in film weight control over that currently achieved in waterbased compound systems.

With the use of at least one damping means, the system provides filmweights within +/-3% of the desired weight. When both damping means areused, the film weight is controlled to within +/-3% of the desiredweight, and additional advantages are obtained, such as reduction in thewater hammer effect with a pressurized feed, thus extending pump life.The use of the one or more dampeners represents a five fold improvementin the ability to control film weights as compared to that currentlyachieved with water based compound systems.

While the present invention has been disclosed with reference to itspreferred embodiments, other embodiments can achieve the same result.Variations and modifications of the present invention will be obvious tothose skilled in the art and it is intended in the appended claims tocover all such modifications and equivalents as fall within the truespirit and scope of this invention.

What is claimed is:
 1. A conditioning system for water based compounds comprising an inlet means for connecting the system to a supply of compound, a first pressure regulation means for compensating variations in the supply pressure, the first pressure regulation means being adjacent to and downstream from the inlet means, a pumping means for circulating the compound through the system, the pumping means being adjacent to and downstream from the first pressure regulation means, a means for filtering coagulum, a connection means for attaching the system to one or more lining nozzles, a second connection means for attaching the system to an exit port of the one or more lining nozzles, a second pressure regulation means for adjusting the line pressure as well as for compensating variations in the pressure of the system, and a return means connected between the second pressure regulation means and the pumping means so as to allow for the recirculation of compound through the system.
 2. The conditioning system of claim 1 further comprising one or more means for damping pressure variations in the system, one or more means for sensing the pressure within the system, and a means for controlling the temperature of the compound.
 3. The conditioning system of claim 2 wherein the one or more means for damping pressure variations is a pressure dampener, the one or more means for sensing the pressure is a pressure gauge and the means for controlling the temperature of the compound is a heater.
 4. The conditioning system of claim 2 wherein one of the means for damping pressure variations in the system is located between the pumping means and the means for filtering coagulum, a first of the one or more means for sensing pressure within the system is located between the first regulation means and the pumping means, a second of the one or more means for sensing pressure within the system is located between the second connection means and the second pressure regulation means and the means for controlling the temperature is between the pumping means and the lining nozzles.
 5. The conditioning system of claim 2 wherein the system controls film weight of the compound to within +/-3% of a desired weight.
 6. The conditioning system of claim 1 wherein the first pressure regulation means is a gravity feed tank connected to the supply of compound by an automatic valve, the pumping means is a double diaphragm pump, the means for filtering as a filter, the second pressure regulation means is a back pressure regulator and the return means is a connector attached to the inlet side of the pumping means.
 7. The conditioning system of claim 1 wherein the system controls film weight of the compound to within +/-5% of a desired weight.
 8. A conditioning system for a water based compound comprising an inlet for connection to a supply of compound, an automatic valve connecting the supply to a tank, the tank being connected to a downstream component of the system at a lowermost portion of the tank so as to supply the compound by gravity to the system, a first pressure gauge downstream of the tank, a pump, a first pressure dampener connected to an outlet of the pump, a filter connected between the first dampener and a heater, the heater having a controller for varying the temperature of the compound as it flows through the heater, an outlet from the heater being attached to an inlet port of a lining nozzle, a connector attached to an outlet port of the nozzle, a second pressure gauge being connected downstream from and adjacent to the outlet port, a pressure regulator selected from the group consisting of a back pressure regulator, a pinch valve and a flow control valve, connected downstream from the second pressure gauge, a second pressure dampener connected to the downstream side of the pressure regulator and a return line connecting the second pressure dampener to an inlet of the pump.
 9. The system of claim 8 wherein the pump is a double diaphragm pump.
 10. The system of claim 8 wherein the dampeners are selected from the group consisting of air activated, automatically controlled bladder dampeners, fixed charge bladder dampeners and flow through dampeners.
 11. The system of claim 8 wherein the heater is a polytetrafluoroethylene lined hose enclosed within a heated jacket.
 12. The system of claim 8 wherein the tank has a level control system for detecting and controlling the amount of compound in the tank within a predetermined range.
 13. The system of claim 8 wherein the pressure regulator is a back pressure regulator.
 14. The system of claim 8 wherein the system controls film weight of the compound to within +/-5% of a desired film weight.
 15. The system of claim 8 wherein the system controls film weight of the compound to within +/-3% of a desired film weight.
 16. A conditioning system for a water based compound comprising an inlet for connection to a supply of compound, a valve connecting the supply to a tank, the tank having an outlet connected to a downstream component of the system at a lowermost portion of the tank so as to supply the compound by gravity to the system, a pump connected to the tank for receiving the supply of compound, a first pressure dampener connected to an outlet of the pump, a filter connected between the first dampener and a heater, the heater having a controller for varying the temperature of the compound as it flows through the heater, an outlet from the heater being attached to a first junction which divides the flow of compound into two or more branches, each branch being connected to a first pressure regulator which is connected to an inlet port of a lining nozzle, an outlet port of each nozzle being connected to a second pressure regulator, the second pressure regulator being connected to a second junction which combines the two or more branches into one flow, a second pressure dampener connected to the downstream side of the second junction and a return line connecting the dampener to a portion of the system between the outlet of the tank and the pump.
 17. The system of claim 16 wherein the pump is a double diaphragm pump, the first pressure regulator is selected from the group consisting of a downstream regulator and a flow control valve; and the second pressure regulator is a back pressure regulator.
 18. The system of claim 16 wherein the dampeners are air activated, automatically controlled bladder dampeners.
 19. The system of claim 16 wherein the heater is a polytetrafluoroethylene lined hose enclosed within a heated jacket.
 20. The system of claim 16 wherein the tank has a level control system for detecting and controlling the amount of compound in the tank within a predetermined range.
 21. The system of claim 16 wherein the first pressure regulators are connected to each of the two or more branches between the first junction and the lining nozzle.
 22. A conditioning system for a water based compound comprising an inlet for connection to a supply of compound, a valve connecting the supply to a tank, the tank having an outlet connected to a downstream component of the system at a lowermost portion of the tank so as to supply the compound by gravity to the system, a pump connected to the tank for receiving the supply of compound, a first pressure dampener connected to an outlet of the pump, a filter connected between the first dampener and a heater, the heater having a controller for varying the temperature of the compound as it flows through the heater, an outlet from the heater being attached to a first junction which divides the flow of compound into two or more branches, each branch being connected to a first pressure regulator which is connected to an inlet port of a lining nozzle, an outlet port of each nozzle being connected to a second pressure regulator, the second pressure regulator being connected to a second junction which combines the two or more branches into one flow, a second pressure dampener connected to the downstream side of the second junction and a return line connecting the dampener to a portion of the system between the outlet of the tank and the pump, wherein the system controls film weight of the compound within +/-5% of a desired film weight.
 23. A conditioning system for a water based compound comprising an inlet for connection to a supply of compound, a valve connecting the supply to a tank the tank having an outlet connected to a downstream component of the system at a lowermost portion of the tank so as to supply the compound by gravity to the system, a pump connected to the tank for receiving the supply of compound, a first pressure dampener connected to an outlet of the pump, a filter connected between the first dampener and a heater, the heater having a controller for varying the temperature of the compound as it flows through the heater, an outlet from the heater being attached to a first junction which divides the flow of compound into two or more branches, each branch being connected to a first pressure regulator which is connected to an inlet port of a lining nozzle, an outlet port of each nozzle being connected to a second pressure regulator, the second pressure regulator being connected to a second junction which combines the two or more branches into one flow, a second pressure dampener connected to the downstream side of the second junction and a return line connecting the dampener to a portion of the system between the outlet of the tank and the pump, wherein the system controls film weight of the compound within +/-3% of a desired film weight.
 24. A process for conditioning and stabilizing water based compounds comprising supplying water based compound to an inlet, passing the compound through a first means for regulating the downstream pressure of the compound, passing the compound through a pump to one or more lining nozzles which selectively open and close so as to draw off compound, passing the compound out of the one or more lining nozzles through an exit port of the one or more lining nozzles, passing the compound through a means for regulating the upstream pressure of the compound, to a return line and recirculating the compound to the pump at a point downstream of the first means for regulating the downstream pressure of the compound.
 25. The process of claim 24 wherein the first means for regulating the downstream pressure of the compound is selected from the group consisting of a downstream pressure regulator and a gravity fed tank; and the means for regulating the upstream pressure of the compound is an upstream pressure regulator.
 26. The process of claim 24 further comprising the step of damping the compound pressure variation downstream of and adjacent to the pump.
 27. The process of claim 24 further comprising the step of damping the compound pressure variation downstream of the one or more lining nozzles, but upstream of the pump. 